Hey everyone, welcome back to CHapter 3. I'm Rachel Mitchell here with Jcuneo, and today we’re diving into the fascinating world of the chemical mind. Or...well, the psychobiology that underpins everything we do.And hi, I'm Jcuneo—professor of psychology, frequent whiteboard abuser, and nervous system enthusiast. Rachel, do you ever realize just how much happens in your body every second, even when you’re just, like, sitting around doing nothing?Constantly! It's wild to think that more than 99 percent of your nerve cells are hanging out right in the central nervous system—that’s your brain and spinal cord, for anyone who’s rusty on the basics.Right. Then we've got the peripheral nervous system, which is like this super busy network running between the CNS and every nook and cranny of your body, from your toes to your—well, earlobes, I guess.Exactly. The peripheral nervous system is actually split up further. A lot of folks mix these up, but there’s the somatic system—which is all about voluntary movement and, of course, pain—and then the autonomic system, which pretty much handles all the behind-the-scenes work, like heart rate and keeping you breathing even when you aren’t thinking about it.That’s right. And the autonomic’s kinda got this sibling rivalry going on between the sympathetic and parasympathetic systems. One gets you all hyped—or freaked out—and the other cools things back down. Think of the sympathetic as the one shouting, “Run! There’s a bear!” and the parasympathetic is, like, “Hey, you made it, let’s, uh, digest lunch and chill.”We love a good analogy on this podcast. And speaking of analogies, Jcuneo, I always remember when you compared a neuron to a human arm in class—dendrites are like your fingers, the cell body is your palm, and the axon is your forearm sending messages away. It’s so much easier to visualize that than just talking about axons and dendrites floating around in the brain!(Laughs) I definitely overuse that one, but hey—if it works, it works. The key is remembering dendrites receive; axons send. Neurons are one-way streets, pretty much.Totally. And just to bring it home, think of Nikita—she pricks her finger, and bam, her hand jerks away before she even realizes. That’s the somatic system at work, moving those muscles on autopilot to protect you.Meanwhile, if your heart’s racing before a big exam, that’s the sympathetic system flooding your body with adrenaline, revving you up for action—or, let’s be honest, existential dread. Okay, moving on—So now that we’ve got the lay of the land, let’s talk about how the messages actually get around. You’ve got these electrical impulses zapping down axons—all very sci-fi—but when it gets to the end, it’s not an electrical handshake with the next neuron. There’s a gap.Yeah, that gap is the synapse. The electrical impulse reaches the terminal button, then gets converted into a chemical signal—otherwise those messages would just hit a dead end. Vesicles release neurotransmitters into the gap, and those molecules cross over, hit a receptor site, and trigger the next action potential.And the exact neurotransmitter that’s released changes everything. Acetylcholine helps you move; it’s the key player when you pick up your coffee mug. If you’re low on it, you might see problems with memory or muscle contraction—think Alzheimer’s, or even something simple like muscle weakness.Dopamine is another big name—move too little, like in Parkinson’s, or have too much, like in schizophrenia...it’s kind of a Goldilocks situation. Not too much, not too little. And let’s not forget serotonin—hello, mood regulation and depression.Yeah, I actually remember a patient case—not going into details, obviously—but this person’s mood and even how they moved started shifting when their dopamine levels dropped. Like, they’d be kind of flat emotionally one day, and then suddenly couldn’t coordinate basic stuff like tying shoes. It was such a clear example of chemistry directly influencing behavior.GABA’s important too, right? It chills out your brain’s activity—think of it like a brake pedal. If you don’t have enough, anxiety can go through the roof. And endorphins...well, those are your natural painkillers. It’s why runners sometimes get that “high”—endorphins are kicking in to block the ouch.And let’s not forget norepinephrine, which literally excites neurons during times of stress. If you’re constantly under stress, those systems can get, well, a bit out of whack. It just shows how brain chemistry is connected to daily experience, not just something locked away in a science textbook.All right, so zooming out—let’s get into brain regions. The brain is like a bustling city with all these neighborhoods, each with a unique vibe. The brainstem is, you know, the “oldest” part—keeps your heart beating, keeps you breathing. Controls things you never consciously think about, unless something's gone really wrong.Then there’s the limbic system, which is your emotion headquarters. The amygdala—think emotional awareness and, let’s be real, occasional rage issues. It gets triggered when you see a threat or even just a really good plate of nachos. The hippocampus, meanwhile, is handling memory—if you can’t remember where you left your keys, that’s the bit to blame.Cerebral cortex is, like, what makes us especially human. It’s this wrinkly outer shell broken up into those famous lobes—frontal, parietal, temporal, and occipital. Frontal lobe is decision-making, personality, voluntary movement—all the executive stuff. Parietal is spatial awareness, which I am not great at, honestly. Occipital is vision, and temporal is for hearing and language.When brain injury happens, the symptoms line up in wild ways. Like, someone with damage to the frontal lobe—maybe they can’t plan or make good judgments, while damage to the amygdala might cause sudden aggression or fear. I had a student, Trevor, who struggled with spatial tasks after a parietal lobe injury, while Sienna was nailing verbal stuff but kind of got lost spatially.Which actually reminds me—so we’ve been using MRI to observe brain activity during emotional responses in lab settings. It’s amazing watching the amygdala light up when someone’s exposed to a stressful image or even just, like, a really embarrassing memory. MRI has changed the game, because you don’t have to guess anymore—you can actually see the brain’s traffic in real time.And that dual-hemisphere thing—left usually handles language, right is where spatial perception lives. That’s why a stroke on one side can radically shift someone’s skills, sometimes even leaving language totally intact but messing up, say, drawing or navigation.Which ties us perfectly to our last big idea—neuroplasticity. The brain isn’t nearly as fixed as we used to think. Especially in young kids, before age five, if one side of the brain is injured, the other can take over language or other tasks. That’s wild.Yeah, but even adults have some plasticity. Like, if the neurons aren’t completely destroyed after an injury, the brain can restore function over time. There are these mechanisms like collateral sprouting—where axons of neighboring neurons grow new branches to compensate—or substitution of function, where another area picks up the slack for a damaged region.That makes me think of Megan’s story—she lost some vision after a stroke, but over a few years her brain rewired itself so she could see blurry shapes again. That’s plasticity in action, neurons finding new routes around the damaged zone.Yeah, it’s—um, what’s the word—neurogenesis? That’s where new neurons are actually created. In adults, it’s pretty much limited to the hippocampus and olfactory bulb, but it’s still proof that adaptation never totally stops.And if you’re wondering how to promote plasticity in your own brain, it’s not rocket science. Keep learning, move your body, practice mindfulness—challenging activities, physical exercise, and stress reduction all support brain adaptation. We really can shape our own brains, even if it’s just a little bit at a time.So that’s about it for today’s whirlwind tour of the chemical mind. Neurobiology is everywhere, it’s in how we think, feel, recover, and learn. Rachel, I guess we’ll have to save our weirdest case studies for next episode?Absolutely, let’s keep a few surprises for next time. Thanks for joining us, Jcuneo—it’s always a blast. And thanks to everyone listening for another deep dive into the brain! We’ll see you soon for even more psychobiology—take care, everyone!Bye Rachel, bye listeners. Don’t forget to exercise those neurons. Catch you all next time.

Episodes

Inside the Chemical Mind